The present invention relates to toner supply devices and image forming apparatuses, and in particular, to toner supply devices that can estimate the remaining amount of toner in a storage container that stores the toner, and to image forming apparatuses provided with such toner supply devices.
In an image forming apparatus, the electrostatic latent image formed on a photoreceptor is developed into a toner image by a developing unit that has a two-component developer comprising a toner and a magnetic carrier. The developer in the developing unit is conveyed to the developing section, and the toner gets adhered to the electrostatic latent image due to the application of a development bias thereby forming a toner image. When the toner is consumed due to development, toner is supplied to the developing section of the developing unit by a toner conveying screw provided inside a toner storage section of the toner supply device. In addition, toner is supplied due to the rotation action of the toner storage container, and a necessary quantity of toner is supplied to the storage section.
When a sensor that is provided in the storage section and that detects the quantity of toner detects that the quantity of toner is less than a prescribed quantity, a detection signal is transmitted to the control section, and the toner is supplied from the storage container to the toner storage section.
However, regarding how much toner is remaining in the storage container, since the storage container is a consumable item, a sensor or others for detecting the remaining amount of toner is rarely provided in the storage container, and some other methods have been proposed.
For example, in Unexamined Japanese Patent Application Publication No. 2005-148238, a technology is described in which the storage container which rotates is mounted detachably to a developing unit, the number of revolutions of the storage container is counted, and the amount of toner remaining in the storage container is estimated based on that number of revolutions or the cumulative time of rotation of the storage container.
Further, in Unexamined Japanese Patent Application Publication No. H4-251879, a technology is described in which a fuse is provided in a toner cartridge, the fuse is cut when the power is on or the like after the toner cartridge is replaced, the value of the amount of remaining toner is initialized, and thereafter the amount of remaining toner is estimated by summing the toner dispensing time.
In addition, in Unexamined Japanese Patent Application Publication No. H10-133466, a technology is described in which the cumulative number of transferred pixels in the image forming section, or the cumulative time of driving the toner supply motor that supplies toner to the developing device is measured thereby estimating the amount of remaining toner.
However, in all the technologies described in the above patent documents, the measurement of the amount of remaining toner is started from the time when a new toner storage container is installed for the first time. Also, in the method disclosed in Unexamined Japanese Patent Application Publication No. 2005-148238, the amount of toner supplied per revolution of the storage container cannot be said to be always constant because of changes in the toner density due to the environmental temperature and humidity, and a large amount of error occurs. Further, generally, considering this error, a warning that the toner is exhausted is being displayed early. The user will be forced to waste if, in this manner, it is judged incorrectly that there is no toner although there is some toner still remaining in the storage container.
In addition, in case the toner gets exhausted on the way of continuous image formation, if there is no new storage container near the user, the user takes out the storage container being used currently, shakes it and installs it again in the machine and tires to start printing. In this case, if the user removes and reinstalls the storage container in mid-course, since an initial setting is made when the storage container is installed in the technology described in the above patent documents, there is a problem that the control section judges that the storage container is a new one in spite of the fact that the storage container is only partially filled and incorrectly detects.
These problems are being caused by the fact that the detection of the remaining amount of toner is being made with the presumption that a new storage container is installed every time.
The purpose of the present invention is to provide a toner supply device that estimates the amount of toner remaining in the storage container before the toner gets exhausted without presuming that the installed storage container is a new one, and to provide an image forming apparatus provided with such a toner supply device.